Slurry colloidal zirconium oxide grinding process



Nov. 24, 1964 w. M. WlLSON ETAL 3,153,331

swam COLLOIDAL ZIRCONIUM OXIDE GRINDING PROCESS Filed May 27, 1963 United States Patent 3,158,331 SLURRY COLLGIDAL ZlRCUNllJM OXIDE GRENDENG PROCESS Wilbert Moody Wilson, Morristown, and William B. Kinyon, Helmetta, Nl, assignors to George W. Helme Company, Helmetta, NJ.

Filed May 27, 1963, Ser. No. 283,493 1 Claim. (Cl. 24l5) This invention relates to a method of producing colloidal particles. More particularly it relates to a method using fluid energy grinding in conjunction with a suitable slurry.

The Trost jet mill employs opposing streams of air to grind particles by head-on collision to particles of colloidal dimensions. Into one of these streams, the inlet stream, is introduced a dry powder. The other stream, the recycle stream, is used to recycle the larger particles from the mill.

This invention is described in conjunction with a conventional Trost mill shown in the accompanying drawing and in which;

FIG. 1 is a vertical section view of the mill showing the flow streams therein by means of arrows and,

FIG. 2 is a section View taken on line 2-2 of FIG. 1 and showing the outlet port from the classification chamher.

The Trost mill is used for what is known as the dry grinding method to produce colloidal particles.

According to applicants improved process, a feed stream of suitable slurry is used in lieu of dry powder.

Thus this invention relates to a wet or semi-wet process of grinding particles using fluid energy as shown in the drawing.

The slurry employed by applicants may be of any suitable liquid such as water, kerosene or other liquid hydrocarbon, glycol or other organic liquid.

This invention is especially suited for grinding particles of metal oxides, minerals or metal to sizes in the colloidal range.

A particular example is in the grinding of zirconium oxide.

The normal dry grinding in the Trost mill of zirconium oxide is impossible since air and zirconium oxide form explosive mixtures.

According to this invention an aqueous slurry of zirconium oxide containing from about 12 percent zirconium oxide to about 20 percent zirconium oxide is useable in this process.

Where less than 12 percent zirconium oxide is used an explosive mixture is formed.

Similarly where over 20 percent zirconium oxide is used another explosive mixture is formed.

At from about 12 percent to about 20 percent solid content a suitable slurry It is prepared. This slurry is poured into the mill at the inlet hopper 11 and is propelled into the housing 12 by means of an air stream from an inlet air stream jet nozzle 13.

The slurry 10 and the air stream at suitable pressure, preferably 80 to 150 pounds per square inch, are mixed in conduit 14 and expand in chamber 15.

The opposing or recycle stream is propelled by air at a similar suitable air pressure from jet nozzle 16 into a conduit 17 and thence into chamber 15. In chamber both streams are expanding streams and collide in headon relationship thereby effecting a grinding action between the colliding particles.

The resulting collision stream is propelled into the housing chamber throat 18 and thence against the curved inside surface 19 of the housing as a peripheral stream.

The stream sweeps around the wall 19 with centrifugal force so that the larger and heavier particles are thrown against or adjacent to said wall 19, with the finer and lighter particles being removed with the air at the exit orifice 20.

These fine particles are in the colloidal range. The heavier particles are conducted down passageway 21 to engage the air stream from nozzle 16 and be recycled until they become so fine as to pass out of the exit orifice 20 as colloidal particles.

The slurry feed must be of such a liquid composition as to be fully vaporized in the classification chamber of the housing 12. Thus the liquid of the slurry of this invention upon expansion from conduit 14 into the grinding chamber 15 is vaporized and in so doing cools the material to be ground. Where this material is very friable as for example, sulfur particles, the cooling effect makes it even more friable on impact collision in the grinding cham ber. Moreover the vapors of the liquid in the chamber assist in absorbing and thereby removing the frictional heat of collision of the particles.

Accordingly by introducing the feed material as a liquid slurry of suitable concentration and suitable specie of liquid a vast improvement over the prior art dry grinding is accomplished.

As an example an aqueous slurry consisting of water and 15 percent zirconium oxide was introduced at a suitable rate into hopper 11 and was propelled by a pound per square inch air jet stream at nozzle 13 into the grinding chamber 15. The water was vaporized by the expansive or venturi effect on passing from small diameter con duit 14 into the large diameter chamber 15. The vapors of the water and the ground zirconium particles of chambers 15 were passed into the large chamber of housing 12 by way of conduit 18.

Again there is an expansive eflect and the liquid vapors become fully dispersed in the large volume of air streams from nozzles 13 and 16.

The colloidal zirconium oxide particles are discharged through exit orifice 20 in an air current containing a small amount of water vapor.

In lieu of water a similar percent of kerosene may be used in the formation of the slurry of this invention.

This invention was described by means of several embodiments showing its versatility of use, but it is not to be limited to these illustrations as it embraces the broad concept of grinding a slurry by use of opposing gaseous propellant carrier streams.

We claim:

The continuous re-cycle process of cold grinding zirconium oxide in a Trost jet mill comprising introducing said zirconium oxide as an aqueous slurry of from about 12 percent to about 20 percent oxide into the inlet air stream of said jet mill, cold grinding said zirconium oxide in the presence of vaporizing water to obtain particles within the colloidal range, separating centrifugally said colloidal oxide from said cold still expanding water vapors to produce substantially dry colloidal zirconium oxide and re-cycling the non-separated particles to further cold grinding.

References Cited by the Examiner UNITED STATES PATENTS 2,735,626 2/56 Trost 24l39 2,846,150 8/58 Work 241-5 ANDREW R. JUHASZ, Primary Examiner. 

